Internal-combustion power plant



Dec. 16, 1930. w. G. NoAcK ETAL 1,785,643

' INTERNAL COMBUSTION POWER PLANT Filed Sept. 15. 1927 i Patented Dec.416,1973() WALTER GUsTAv NoAcKANn JEAN DE F'REUDENREICH, o F BADEN,SWITZERLAND INTERNAL-COMBUSTIO POWER PLANT Application filed September15, 1927, Serial No. 219,734, and in Switzerland April 25, 1927.

It has already been proposed to produce the working fluid for gasturbines in special machines in which the explosive mixture is given acertain amount of compression, exploded or U burned' and then partlyexpanded. These operations are conducted under high pressures andtemperatures, and for this purpose the reciprocating engine has provedmore 1 suitable than the turbine. The production of the working fluid istherefore preferably carried out by reciprocating engines, of which theso-called free piston (or iiying piston) engine is to beparticularlyrecommended. Free piston engines have the advantage over thecrank and connecting-rod type in having n0 connecting rod, crank shaftor bearings, and are inconsequence cheaper and mechanically simpler,allowing higher piston pressures and piston velocities, and ahigherfstroke perio- ,39 dicity. These attributes are of particularimportance in plants of the above description,

p since the production ofthe working fluid is an auxiliary function andthe machine serving this purpose is only an auxiliarymachine and Zrshould therefore be simple and inexpensive in design. The main engine inwhich the working fluid is made to do useful work is the gas turbine.The ordinary type of free piston engine having no crank or flywheel isuneven in operation, has very littleoverload capacity and 1s easilystalled; In order to overcome these drawbacksit has already beenproposed to couple the freepiston engine to a reciprocating electricalgenerator, which is connected either to a large electrical system or toa Viiywheel generator which takes over the equalizing functions of aflywheel and by virtue of its inherent synchronizing power ensures .uni-4 form running of the free piston. engine. By suitably designing theelectrical equipmentit is also possible to increase the workingperiodicity ofthe reciprocating part of the machine above thatobtainable when using `the piston forces alone.

The present invention relates to an internal combustion power plant inwhich the working substance, consisting of very hot gas under highpressure, is produced in a recipro- 5 eating engine and expanded to douseful work in a gas turbine, the reciprocating engine being of the freepiston type and coupled to a reciprocating elec trical generator for thepurpose of securing uniform running. The current obtained from thisgenerator may be used to drive a motor for operating other auxiliarymachines, or the two generators, i. e.

the reciprocating generator and the rotary generator driven by the gasturbine, may be operated in parallel. In either case the primary obj ectpf ele machines is to ens ctrically connecting the two ure the uniformworking of v the free piston engine. Should the free piston engine fallout of step, or be in danger of stalling for example owing to ignitiontrouble or other reasons, then either the motor driving the auxiliaries(which would then work as a generator) or the main generator would actas a flywheel ditions had been until 'proper Vworking conrestored.

To secure the necessaryv reliability for the gas turbinewith thematerials at present available, it is essential thatl the working Huidshould not exceed a certain maximum temperature. The less'the expansionin the first row of nozzles the lower will be this maximum temperature.

In order that the allowable temperature for the blades shall not beexceeded avoid using rich it is necessary either to mixtures or to coolthe exhaustn gases as they leave the internal combustion engine by theaddition of cold air. This may be performed in a mixing chamberimmediately before the gas turbine. same result is obtainable by anabundant use The compressor as small as possible the air should bepre-compresse called superchar d. For this purpose a so-v ging blower isemployed which may be either driven bya motor whichdraws its currentfromcthe reciprocating generator, or cou or gas turbine.

pled to ther main generator The simplest arrangement of plant isobtained when no attempt is made to use the reciprocating generator forpower supply purposes its function being confined to that of astabilizer Jfor the free piston engine. In this case the whole of thepower developed by the free piston engine is applied to the compressionof air in the piston compressor, and the reciprocating generator,although electrically coupled either to the main electrical machine orto a `special flywheel generator, runs practically unloaded. A transferof electrical energy between the two machines takes place only if thestrokes of the free piston engine commence to lead or lag on `theuniform rotational motion of the main generator or aforesaid flywheelgenerator. Such an arrangement permits the 'reciprocating generator (andflywheel generator) to be designed for a mere fraction of the powerdeveloped by the free piston engine, sincethe full output is onlyrequired for extremely short periods of time, for example, during a fewstrokes or even a portion of a stroke, and under these conditions theelectrical equipment may be safely loaded up to many times its normalrating.

The production of working fluid for a gas turbine would not ordinarilybe carried out in a single free piston engine, but a number of suchunits would be installed. These units would be electric-ally coupled bymeans of their associated reciprocating generators and uniform workingcould then be ensured by a single rotary generator, or,l in the event ofpower for driving purposes being required from the reciprocatmggenerators, a single motor would suffice. It is then an advantage todesign the rotary generator or motor as a polyphase machine and toconnect each phase with one or more single-phase reciprocatinggenerators. This will also ensure that the motions of the reciprocatingparts of the free piston engines are in a definite phase relationship.For example by making the rotary generator or motor a three-phasemachine the motions of the tree piston engines are fixed at 1200 apartand practically complete balance of the moving parts is obtained.

Two examples of internal combustion power plants embodying the presentinvention are i'illustrated diagrammatically `in the accompanyingdrawings. 1

Figure 1 shows a plant in which the free piston engine which exhaustsinto and drives a gas turbine, supplies energy to a reciprocatinggenerator, the current from which is passed to the main generator towhich the compressor for scavenging and supercharging the free pistonengine is also coupled.

Figure 2 shows a modified arrangement, in which the power-developed bythe free piston engine is employed to drive a piston type compressor,while the reciprocating generator is used simply to secure uniformity ofWorking.

In the two figures the reference character 1 denotes the tree pistonengine, 2 an equalizing'chamber for the exhaust gases, 3 the gasturbine, 4 the main generator, and 5 ablower for supplying scavengingair or air for combustion, which latter may be more or lesspre-compressed. The pistons 6 and 7 are attached to the field magnet 8of the reciprocating generator by means of piston rods. Thereciprocating motion of the field generates an alternating current inthe windings (not shown in the drawing) of the stator 9 and this currentis led through the conductors 10 to the main generator 4, where .itsupplies the power for ndriving the blower 5. A

In the plant shown in Fig. 2 the free piston engine drives a piston typecompressor having pistonsll and 12 carried on the same rods as the eldmagnet 8 of the reciprocating generator. This latter does not supplypower for external purposes, but drives an auxiliary electrical machine13 which is provided with a flywheel 14 to increase the inertia of therevolving masses. A blower 5 coupled to the main generator is used topre-compress the air supplied to the piston compressor in order topermit a shorter stroke to be use-d. This air is further compressed bythe said piston 'compressor and is then used as scavenging andcombustion air in the free piston engine. The exhaust gases from thelatter, which are still at a high pressure and temperature, are thenpassed on to the gas turbine 3.

The auxiliary machine 13 is coupled to elec-A trical machine 15 which iselectrically connected to the main generator by the leads 16. Thismachine 15 enables surplus energy to be transferred to or if necessarywithdrawn from the main generator, even whenthe periodicities of thereciprocating and main generators are not the same. This condition wouldarise, for instance,if the stroke periodicityof the free piston enginewere lower than the frequency ofthe system supplied by the maingenerator.

Instead of a single free piston engine there may be any number of suchunits, all connected to the aforesaid main or auxiliary generator. Asbefore, uniformityof working is obtained by the action of the equalizingcur- .rents which are developed whenever the motions of thereciprocating generators are advanced or retarded with respect to theuni- 'orm rotational motion of the single main or auxiliary generator.

What we claim is:

1. Internal combustion power. plant comprising, in combination, a gasturbine, an electric generator driven by said gas turbine, areciprocating engine of the free or flying piston type theexpandedworking Huid of which operates the gas turbine, a reciprocatingelectric generator driven by the aforesaid reciprocating engine, andelectric coupling means between the said reciprocating electricgenerator and the electric generator driven from the gas turbine, as andfor the purpose set forth. i

2. An electrical generating plant comprising a turbine, a rotaryelectrical generator driven thereby, a reciprocating engine, areciprocating generator driven therefrom, electrical means coupling saidgenerators, said coupling means including an electrical machine of therotary type connected to the reciprocating generator, a ily Wheelmechanically coupled to the said electrical machine, and a secondelectrical machine, the latter machine being electrically connected Withthe rotary generator. i

3. An electrical generating plant comprising a turbine, a rotarygenerator driven by the turbine, a reciprocatin engine, a reciprocatinggenerator driven t ereby, means for electrically coupling thegenerators, a blower coupled With the rotary generator, a compressorconnected With the reciprocating generator, said coupling meansincluding an electrical machine connected with the reciprocatingenerator, a second electrical machine, a flyw ieel mechanicallyconnected to the second machine, said second machine being electricallyconnected Witli the rotary generator.

In testimony whereof We have signed our names to thisspecication.

`WALTER GUSTAV'NOACK. JEAN DE FREUDENREICH.

